Rust inhibitor for light petroleum products



Patented Mar. 24, 1953 SATS RUST INHIBITOR FOR LIGHT PETROLEUM PRODUCTS Phillip S. Landis, Mickleton, and Elwood B.

Backensto, Woodbury, N. 3., assignors to Socony-Vacuum Oil Company, Incorporated, a

corporation of New York No Drawing. Application September 20, 1951, Serial No. 247,552

9 Claims.

The present invention relates to the prevention of the formation of rust on metallic surfaces in contact with mineral oil products and more particularly to prevention of a formation of rust on metallic surfaces in contact with mineral oil products such as gasoline, naphthas and burning oils.

The problem of preventing the formation of rust on metallic surfaces in contact with mineral oil products has received considerable attention in the past decade with respect to-those fractions of mineral oil which are used for lubricating purposes. However, the prevention of the formation of rust on metallic surfaces in contact with what may be termed light products, 1. e., naphtha, including thereby gasoline and kerosene and burning oils, has not received so much consideration. While the problem may seem to be the same, nevertheless the problem of preventing the formation of rust on metallic surfaces in contact with naphthas and the like presents factors which are not encountered when confronted with the problem of preventing the formation of rust on metallic surfaces in contact with lubricating cuts of mineral oil.

One of the most important limitations upon the use of a rust preventive in gasoline, for example, is the limitation that the color of the product must be the same as that of the unprotected gasoline; i. e., the rust preventive must not cause a color change in the gasoline by reaction with the hydrocarbon constituents of the gasoline, dyes, components of tetraethyl lead fluid, anti-oxidants, etc., normally contained or added to gasolines. Furthermore, the rust inhibitor must be one which has no appreciable effect upon the octane rating or any of the other specifications under which the gasoline is sold.

Another factor which is of relatively no importance when considering the formulation of a lubricating oil is that of the effect of extreme pressures on the separation or other action of the rust preventive. Thus, for example, it is well known that products such as gasoline, kerosene and burning oils are in many instances transferred from the refinery to distributing points via pipe lines. Pressures as high as 1200 p. s. i. may be encountered in such pipe line transportation. Consequently, it is essential that the rust preventive remain with the petroleum cut regardless of the pressure to which the cut is subjected.

Another factor controlling the selection of a 2 rust preventive for mineral oil fractions, other than lubricating oil fractions, is the tendency of some known rust preventives to cause the formation of emulsions. Rust preventives which tend to emulsify the water present with the mineral oil fraction are not useful because they tend to hold unusually large amounts of water in the petroleum products.

Indicative of the problem presented in preventing the formation of'rust on metallic surfaces in contact with gasoline, kerosene, burning oils and the like is the fact that of 51 materials tested, 50 failed to provide the protection required at concentrations commensurate with practical limitations. Of the 50 that failed, failure was due to a color change in the gasoline in 18 instances. Of the remaining 32, '7 failed because of their emulsifying action and the remainder failed to provide the required protection at practical concentrations. Thus, it is manifest that although a large amount of information has been obtained uponthe solution of the problem of preventing the formation of rust on metallic surfaces in contact with lubricating fractions of mineral" oil, nevertheless the problem of preventing the formation of rust on metallic surfaces in contact with naphthas, burning oils and the like still remains to be solved.

An important limitation upon the use of a rust preventive in gasoline is its effect upon. gum formation. As a generalization, it can be said that rust preventives are non-volatile in nature, and increase the amount of gum formed by the amount of rust preventive added. Consequently, a rust preventive useful in gasoline is one which is effective in concentrations not more than about 0.008 weight per cent of non-volatile residue. Accordingly, it is an object of the present invention to provide a gasoline, kerosene or burning oil fraction of mineral oil containing an amount of rust preventive not substantially in excess of about 0.008 weight per cent non-volatile residue.

It has now been discovered that dimeric acids are compounds which satisfy all of the requirements of a rust preventive for naphthas and burning oils.

A dimer, as defined in Hackhs Chemical Dictionary, is a condensation product or polymer of two molecules. Thus, when two molecules of a polyethenoid mono-carboxylic fatty acid condense to form a di-carboxylic acid, the product by definition is' a dimer, or the monocarboxylic acid is said to be dimerized. Similarly, the condensation of a molecule of one polyethenoid monocarboxylic acid with a molecule of a second polyethenoid mono-carboxylic acid forms a dimer which is a di-carboxylic acid.

In general, the dimeric acids have been produced by heat polymerization of esters of the mono-carboxylic acids to esters of the dimeric acids followed by hydrolysis. The glycerides have also been heat polymerized and the product hydrolyzed to yield the free dimeric acids. Recently, Goebel in U. S. Patent ,No. 2,482,761 disclosed-that the free fatty acids can be polymerized. Briefly, Goebels process comprises preparing unsaturated fatty acids by hydrolyzing a fat or oil for example, soya' bean fatty acids, adding a small portion of water, and heating in a pressure vessel until substantially all of the diand tri-unsaturated fatty acids present ,polymerize. The resultant product can then be heated at reduced pressure, to-distill off vaporizable constituents, which include mainly saturated acids and mono-unsaturated acids. A temperature of atleast 260 0. must be used and -preferably from 330 C. to 360 C. and a heating period of 3 to 8 hours to produce substantially complete polymerization of diand tri-unsaturated material. Numerous catalysts can be employed but are not necessary. Among the catalysts which can be used are mercuric acetate, lead acetate, anthraquinone, and Raney nickel.

Thus, for-example, as described in U. S. Patent No. 2,482,761, 300 parts by weight of sardine oil having an iodine value of 18.8 were pressure split with 600 parts of water at 260 0. Three treatments of 1 /2, and /2 hour duration were used with 100 parts of the water employed in each treatment.

Water was withdrawn and the wet acids were heated to 350 C. at a pressure of 25.0 pounds per square inch for 4 hours.

The product was then heated at'reduced pres- ..sure to distill ofi unpolymerized material yielding 44 by weight of a residue having an iodine value. of 86:3 and a neutralization equivalent of .386.

In a similar manner, as described in the aforesaid pa'tent, linseed :fatty acids, ,soya bean fatty acids and the fatty acids of other drying or semidrying oils can be polymerized to produce what the patentee names dimeric acids. The patentee states :that byhis process larger yields of dimeric acids are formed and less of the trimeric and higher polymeric acids are formed.

Another source of dimeric acids is the still residue of the dry distillation of castor oil in the presence of sodium hydroxide. An analysis of the fatty acids from castor oil has been reported in Chem. Abs. 34, 3521 as follows:

Per cent Ricinoleic acid 8'7 Oleic acid 7 Linoleic acid 3 Saturated acids 3 Distillation of the aforesaid still residue yields .two approximately equal fractions, the distillate and a second still residue.

d The material of the first still residue of the dry distillation of castor oil in the presence of sodium hydroxide has the following properties:

Lot 1 Lot 2 Neutralization No 164 159. 9 Bromine No.... 120.7 19. 4 Kinematic Viscosity at 100 13096 1373 Lovibond color 750 750 10 A. P. I. Gravity, degrees".. 14. 6 15. 2 Specific Gravity 0. 9685 0. 9646 The dimeric acids on the basis of the present data are mono-cyclic or dicyclic hydroaromatic dicarboxylicacids depending upon the degree of is formed:

0 g(CH1)1PJ-OOHJ on H i i CH3(CH2)3C=CCH H? OHa(CH2)aCH HC FORMULA I This compound after hydrolysis yields the .free acid having the structure shown :in Formula .II,

or isomers thereof:

FORMULA II The octadecadienate estersdimerize by"1,4.-diene addition to a compound having the structure shown in III, or isomers of it.

CHa(CH) H H a 5 \O% FORMULA III This dimer upon hydrolysis yields the free acid having the structure given in Formula Il/Zor isomers of it. :2

When one of the free octadecadienoic or octadecatrienoic acids are polymerized as described in U. S. Patent No. 2,482,761, the patentees dimeric acids have the structures shown in Formulae II and IV, or isomers of them.

Castor oil contains ricinoleic acid in the form of a glyceride. The most important pyrolytic reaction of ricinoleic' acid and its esters is that of dehydration to produce octadecadienoic acids. Therefore, in the dry distillation of castor oil in the presence of sodium hydroxide the higher boiling portion, i. e., the still residue is a mixture of polymerized octadecadienoic acid derived from the ricinoleic acid and the linoleic acid present in the castor oil.

From the foregoing a generic formula for the dimeric acids of the present invention can be written. Thus, as an example of an octadecadienoic acid, the polymerization of linoleic acid is illustrative. Linoleic acid or A9,10,12,13-octadecadienoic acid is present in peanut, palm, olive, teaseed, kapok etc., oils in amounts of les than 25%. Oils such as corn germ, cottonseed, sunfiowerseed, poppyseed, sesame, etc., contain 40% to 60% linoleic acid. The linoleic acid obtained from the great majority of plant sources is A9,10,- 12,13-octadecadienoic acid.

When A9,10,12,13-octadecadienoic acid is dimerized in the absence of other polyethenoid acids, either as an ester or as the free acid in the manner described in U. S. Patent No. 2,482,761, a reaction which takes place can be illustrated by the following formula:

with a shift in the double bond this becomes:

where R::CH3(CH2)4 and R'=(CH2)7COOH. However, for the various isomers of linoleic acid R will have a different value. Thus artificial linoleic or octadecadienoic acids have their origin in three natural sources, (1) fatty acids more highly unsaturated than linoleic acid, which on partial hydrogenation form isomeric acids, (2) normal linoleic acid whose double bond may be shifted by isomerization catalysts and (3) monoethenoid hydroxy acids, such as ricinoleic acid, which on dehydration form an additional double bond. For example, ricinoleic acid dehydrates to two isomeric linoleic acids, A9,10,11,12-octadecadienoic acid and A9,10,12,13-octadecadienoic acid. When A9,10,11,12-octadecadienoic acid dimerizes in the absence of other polyethenoid acids, the resulting dimeric dicarboxylic acid has the formula where R is CH3 (CH2) 4- and R is -(CH2) 7COOH However, when the monocarboxylic acid is A8,9,- 12,13-isomer the dimeric dicarboxylic acid has the structure where R is CH3(CH2) 4 and R is (CH2) eCOOH Similarly with the A9,10,13,14-isomer the dimeric dicarboxylic acid has the structure where R is CH3(CH2)3 and R is -(CH2) 7COOH. It follows that when the 'A9,10,l2,l3-isomer is dimerized R is CH3 (CH2) 4- and R is where R is CH3(CH2)4 for the A9,1 0,12,-13-isomer and the A9,10,11,12-isomer, and CH3(CH2) 5 for the A8,9,12,13- and A9,10,13,14-isomer, R is carboxylic groups of the monocarboxylic acid and the nearer carbon of the nearer double bond. From this it follows that th generic formula for dimeric acids derived from a single (ii-ethenoid monocarboxylic aliphatic acids is R-CH2C{HECIIR *8 When 1A9,'10;11,12,13,14-octadecatrienoic acid .is the sole acid polymerized to form the dimeric dicarboxylic acid the condensation can be pictuned as occurring asfollows': H1 H1 H H H H is 17 1s 14/13 12 111 10 :9

which the shift of the double bond at 11a and 11 becomes The generic formula for the dimeric 'dicarboxylic acids derived from the dimerization of where R is CH3 CH2) nand .R' is (CH2)mCOOH and n and m have the values given hereinbefore. When polyethenoid acids, i. e., triand greater ethenoid acids such as n-linolenic acids are dimerized, the dimeric acids obtained are bicyclic dicarboxylic acids having the formula when only a single acid undergoes polymerization. Typical of the triethenoid acids are linolenic or A9,10,12,13,15,16-octadecatrienoic acid and elaeosteari'c or A9,10,11,12,13,14-octadecatrienoic acid. When A9,10,12,13,15,l6-octadecatrienoic acid is the sole polyethenoid acid present it polymerizes to form the dimeric dicarboxylic acid the condensation can be pictured as occurring as follows:

I I 15 14/13 12 {11 1o '9 with a shiftv of the double bonds at 15 and 16 p the formula of the dimeric acid becomes:

individual triethenoid octadecatrienoic acids is where R is CI-I3(CI-I2) and R is (CH2) 'TCOOH 40 A well known source of these dimer'ic acids is the product sold by Emery Industries, Inc., and said to be dilinoleic acid. In the literature published by the Emery Industries, Inc. the properties of this product are given as follows:

Neutral equivalent 290-310 Iodine value 80-95 Color Gardner 12 (max) Dimer content Approx. 85%

Trimer and higher Approx. 12%

Monomer Approx. 3%

Tests of several batches of material supplied by this producer indicate that the properties of this product are within the limits set forth hereinafter: 1

Specific gravity, A. P. I 15-151 Specific gravity, 1360/ 0.9665 0 Color, Lovibond 35 Kinematic viscosity 100 F., centistokes 24624666 A. S. T. M. bromine No 39.3 Neutrality No. 136.8-1904 Iodine value 67-86 It will be noted that the dimeric acids available from the 1 Emery Industries, Inc, contain approximately dimeric acids and about 12% trimeric, and higher polymeric acids and the second still residue of the dry distillation of castor oil in the presence of sodium hydroxide contains about 45-50% of the dimeric acids and about 50% of the trimeric and higher polymeric acids. Since neither of these industrially available products is 100% dimeric acids it is manifest that materials containing more highl polymerized acids than the dimeric acids can be used. However, it is to be noted that these materials contain only small amounts, say less than of the monocarboxylic or unpolymerized fatty acids and saturated acids.

Accordingly, preferred materials are those containing not more than about of unpolymerized unsaturated fatty acids and saturated fatty acids. -In general, the content of dimeric acids and trimeric and higher acids should be of the order of at least about 85% with the dimeric acids representing at least about 50% of the dimeric and higher polymeric acids. Thus, the Emery Industries dimeric acids contain about 85% dimeric acids while the second still residue of the dry distillation of castor oil in the presence of sodium hydroxide contains about 46.8% dimeric acids. Those skilled in the art will recognize that the lower the concentration of dimeric and higher polymeric acids the greater the amount of the mixture required to provide the protection against the formation of rust. Consequently, a point will be reached at which the concentration of non-polymeric acids will be sufiiciently low to require the use of such an amount of the mixture containing the polymeric acids that the non-volatile residue left in gasoline for example will exceed that permitted by the specifications. Accordingly, the concentration of dimeric and higher polymeric acids in a mixture should be high enough that eifective protection against the formation of rust is obtained but the non-volatile residue of the protected petroleum fraction does not exceed that permitted by the specifications.

The eflicacy of dimeric acids as a rust-preventive in gasoline, naphthas and burning oils was determined 'by three tests. One was the modified A. S. T. M. D665-47T test, which has been stated to be more severe in many respects than actual pipe line conditions in that it is run at a higher temperature (80 F.) than is usually found in a pipe line, with a much higher relative amount of water present and under conditions such that the test materials are saturated with oxygen at all times. It has been said that test specimens exposed to the severe rustin conditions of this test for two days are rusted to substantially the same degree as those exposed in a products pipe line for 30 to 60 days. The A. S. T. M. test was modified to the extent of lowering the test temperature from 140 F. to 80 It is to be understood that all evaluations were made in sets of ten samples, one sample being an uninhibited petroleum fraction control blank which tailed in all cases. The test was only rated as passing when the test specimen in fractions boiling above gasoline showed no rust below or above the interface after the test period.

However, when testing protected gasoline and other light products, no significance was placed on the appearance of several rust spots above the interface of the test coupon. Evaporation of the sample and spraying of the sample with water above the level of the liquid being tested was unavoidable. Consequently, rust on the unprotected part, i. e., the area above the oil surface of the coupon, has little meaning.

The rust preventive was also subjected to a static rust test. The static rust test has been described by Baker, Jones and Zisman, 'IEC 41, 137 (1949). In this test a steel plate cut in the shape of an equilateral triangle and pressed to form a shallow cup in the center is immersed in the test oil. After standing in the test oil for one hour in 100 F., a droplet of distilled water is placed on the center of the metal specimen and the test continued until visual rust appears on the metal surface. In this test the dimeric acids were the most effective of all materials tested in concentrations of 0.0011 to 0.0053 weight per cent.

To determine the effect of pressure upon the rust-preventing efficacy of the dimeric acids, 2. modification of the A. S. T. M. rust test was used. This test was carried out as follows: a rustproof alloy pressure bomb equipped with a rocker arm for agitation was used. A. S. T. M. steel test coupons, fastened to the bomb head thermowell, were used. Pressure was obtained by injection of mixtures of nitrogen and oxygen gas as indicated F. for 48 hours and employing distilled water. in the following table:

T f fi t l l d. imeo 151 e Additive f j i il Test, Water, Remarks Hours Percent Volume 02 Total Umnhibited 1300" }8 48 10 Slight rust. Do 165 1,20 80 48 20 Do. 0.0011 percent dimeric acids 15 1,200.-.. 80 48 20 No rust.

o 165 1,200.-- 80 48 20 Do. 0.0022 percent dimeric acids 15 1,20 80 48 None Heavily mill scaled coupon used.

1 Total pressure attained by adding nitrogen. R No apparent change in amount of mill scale. Coupon weight before test, 93.3419 gm.; coupon weight after test, 93.3429 gm. When samples of finished gasoline containing normal amounts of dye, tetraethyl lead, anti-oxidants, etc., and the indicated amounts of dilinoleic acid were subjected to the aforesaid A. s. T. M. test, the following results were observed:

and research method of finished gasoline as the following tabulation makes manifest.

Effect of dimer acids on properties of finished ceases gasoline No. 2 fuel oil did not afiect the gravity, A. S. T. M. boiling range, aniline cloud point, diesel index, Concentration f Additive flash, pour point, sulfur, corrosion, carbon resi- 6 due, B. S. 8: W., ash or the factors of the fuel I None 0 3 e oil stability test, as is manifest upon study of the Percent pefcelvlt following tabulation:

s T M O I 7 Effect of dzmer (roads on properties of No.- 2 ,1-

13? 95 94 95 fuel ozl 121 121 121 ear is a a I awZIII: 191 191 191 Concentration of Additive 3 a: a as goZiIIIIIIL- I 252 250 250 Dimefic Acids None 273 270 272 15 299 29s 29s 339 335 338 Gravity O A. P. I 36.3 EP 409 403 405 Dist., A. .'r. M., F Rea, percent 96 5 96.5 96. 5 IBP Rea, percent 2 1. 2 1. 2 Loss, percent 2. 3 2. 3 2. 3 Color Glass Dish Gum, mg./100 00.. 1.6 1. 7 4.4 Octane Rating: 2

Motor method base 71. 7 71. 6 71. 7 +1.0 cc. TEL/gal 77. 9 77.8 78. 4 +3.0 cc. TEL/gal 83.0 82.9 82. 0 Research method base..-. 74. 0 74. 0 74. 0 +1.0 cc. TEL/ge1 s2. 1 82.0 82.0 +3.0 cc. TEL/gal 87.5 87. 2 s7. 4

Similarly, the addition of the dimeric acids to 1 No noticeable change.

1 Finished blend except for TEL.

flash, sulfur, B. S. & W., smoke point, or burning at F quality as the following tabulation clearly estabpereent Wt.

Sulfur, percent wt Copper Strip Corrosion, 3 hrs.

Carbon Residue (on10%Bott.), 0.10

Passing.

fishes: Ash, percent wt Nil Efiect of dimer acids on properties of kerosene Concentration of Additive Dimei-ic Acids None 0.0011 wt. percent 0.0053 wt. percent Gravity, A. P. I 45. 0 44. 9. Dist. A. S. T. M., F.:

rise. 335

Rea; percent. Res, percent Loss, perceut Color, Saybolt S/V Catalytic Color Stab1 1 y Good... Flash, Tag, F 116 Sulfur, percent Wt 0. 047 Copper Strip Corrosion,

3 hrs. at 212 F 55 B. S. & W., percent wt Nil Smoke Point, mm 8 Burning Quality:

24 Hour Burn- Chimney Light White Light White Wick Incrustatron. Hard Granular Hard Gran Deposit.-- Light Even Mushroom N Flame Shape Good 48 Hour Bnrn- Chimney Duty White Heavy White WlOk Incrustatmn. Hard Granular Hard Gran; Slight Gloss...

Deposit Heavy Uneven Heavy Uneven; Tend to ump. Mushroom N N Fibre weakened weakened Char Flame Shape Held shape well Held shape well Change, hf e Change, wth Oil Consumed, cc. hour. 50.8.-

Light White.

Hard Gran. Heavy, Fairly even. None. Good. 7

Heavy White.

Hard Gran.; Slight Gloss.

Heavy Uneven; Tend to lump.

None. weakened.

eld shape well.

assesses" Concentration of Additive Neutraliza Bromine tion Number Number 0.0011 wt. 0.0053 Wt. Dlmenc Aclds None percent percent Castor Oil Polymer Acids:

Fractlon 1 241. 7 20. 5 Fraction 2 159. 6 l7. 6 B. S. & W., percent wt Trace Trace Trace. Fraction 3 182. 3 21. 2' 'lSD Fuel Oil Stability Test: Fraction 4 Test before aging- Residue 139. 4 20. 4

Color, NPA 2% 2%- 2 Emery Industries Dimer Acids: 600 Gum 7. 9 8. 2 7. 7. Fraction 1 175. 0 44. 1 Test after aging 10 Fraction 2. 189. 8 40. 0 3%. Fraction 3 186. 5 36. 5 7. 4. Residue 153. 6 30. 4

4. 6. 0. These materials were subjected to the A. S. T. M. rust test at 80 F. and the following The residue from a dry distillation of castor oil data obtained:

Calcai- Concentration in Finished Gasoline a e Rust inhibiting Material Molec- 'glgg 0.001% 0.002% 0.004%

Emery Industries Dimer Acids... pass Castor Oil Polymer Acids:

Lot 1 Lot 2 do. Emery Industries Dimer Acids:

l 450 do 540 (50 pin pts. rustgu 690 (12 pin .pts. rust 700 pass Castor Oil Polymer Acids: f 1 l S1 Fraction 1--- 360 rust Fraction 2... 435 pass--- Fraction 3 520 .do Fraction 4 Residue 600 pass pess pass.

1 Uninhibited finished gasoline shows severe rust in this test. 1 As defined hereinbefore, column 10, lines 17-23.

in the presence of sodium hydroxide was subjected to distillation in a molecular still and the following data obtained:

TABLE I Pressure Calculated 1 Fraction 0 Weight I Number g fi gggfig percent g 'i f 0. 015 8. 8 360 0. 013 23. 6 435 0.015 14.4 i 520 4 0.025 3. 2 Residue 50. 0 3 600 1 Molecular weights were extrapolated from molecular still distillation temperatures. Analytical boiling point elevation methods of determining molecular weight yielded unusually high molecular weight values indicating molecular association.

I Predominately dimeric acids.

3 Predominately trimeric acids.

More than.

Emery Industries dimer acids when subjected to distillation in a molecular still yielded the following data:

Pressure Calculated 1 Fmtmn B. P. 0. millimeters Weght Molecular Number of Mercury percent weight 160-200 0. 020 33. 7 450 200-240 0. 020 54. 2 7 540 3 240-290 0. 020 7. 2 3 690 Residue 4- 9 4 700 1 See footnote to previous tabulation. 2 Predominately dimeric acids.

3 Predominately trimeric acids.

4 Trimeric acids and higher.

More than.

It has been established hereinbefore that the addition of about 0.0006 to about 0.008 weight per cent of dimerized fatty acids; 1. e., dimer acids to petroleum oil fractions other than lubricating fractions inhibited the formation of rust on ferrous metal containers in contact with so-protected petroleum oil fractions. This is rather surprising when it is considered that a turbine oil containing six times the maximum amount of dimer acids which it is now proposed be added to non-lubricating fractions failed to provide any protection. This is established by the following data:

unique in the field of application of the present invention is the fact that undimerized fatty acids fail to prevent the formation of rust in the modified A. S. T. M. test whereby the eflicacy of dimcrized fatty acids was determined. This is aasacam 15 manifest after study of the data presented in the following tabulation:

D: A.dimerizedfatty acidsl *A-Qmigztnre of undimerizcd'fatty acids: 53 percent linoleic acid, 34

percent oleic acid, '2 percent 'linolenic acid and ll percent'saturatedi rnixture of undimerized fatty acids: 40 percent linoleic acid, 50 percent oleic acid, 4 percent linoleic acid and 6 percent resin acid. nn'xture of 012 to C22 aliphatic monocarboxylic acids, about 50 percent saturated acids and the balance unsaturated acids.

. Modified A. S. T. M. D6 65-47T, distilled water, 48 hours 80 F.

.The dimerized fatty acids are unique in another-characteristic; i.-e., failure in the A. S. T. M. rust testfor turbine oils (using dislzilled water) at concentrations much higher than the maxi mum permitted in gasoline for example. Thus, while dimerized fatty acids give satisfactory protection in gasoline, naphtha, fuel oil and like fractions of petroleum other than lubricating oil fractions inconcentrations as low as 0.001 weight percent, when subjected to the A. S. T. M. test for..tixrbineoilprotection at 140 F. dimerized fatty acids fail even in concentrations as high as" weight per cent. f

'Ihe.foregoing-discussion provides a basis forstating .that .the. present invention provides aj means of inhibitingthe rusting of ferrousmetals innontact 'with"non1 ubricating fractions of mineral oil by incorporating an amount of dimerized fatty acids, designated by Go'ebel in U. S. Patent No. 2,482,761 at colunm 7, lines 8 to 20 as dimeric acids, in non-lubricating fractions of:minera1 oil effective to inhibit rusting of ferrous metals with which the mixture is in contact. The rusting of pipe lines-and storage vessels fabricated from ferrous metals .is inhibited when the non-lubricating fraction of mineral oil containing an effective amount oi dimericacids is transported or storeduin suchcontainers. a

The 'dimericacids can be'characterized as being-dicarboxylic acids having either one substituted six-membered hydroaromatic ring or havin two fused sin-membered hydroaromatic rings the one of which does notcarry the two carboxylic acid groups being disubstituted. The dimeric acids are further characterized by having the two carboxylic acid groups attached to a single six-membered' hydroaromatic ring through a plurality of (CH2)- groups the num-- ber'of such groups being dependent upon the number of such groups between the carbon atom of the'carboxylic acid group and the nearer carbon of the nearest double bond of the monocar-- 16 group. Consequently, the dimeric acids of the rust inhibiting material when prepared from the individual monocarboxylic acid are represented by two formulae and n is a small number one more than the number of CH2: groups between the terminal CHsgroup and the nearer carbon of the nearer double bond of the diethenoid monocarboxylic acid from which the dimeric acid is derived and m is a small number representing the number of CH2: groups between the carbon of the carboxylic group and the nearer carbon of the nearer double bond of the diethenoid monocarboxylic acid from which the dimeric acid is derived, and

where R" is CH3(CH2)n and R' is cH2) mCOOH and n and m have the same significance as -be fore.

It follows that the present invention is the provision of a new composition of matter com prising a normally liquid non-lubricating fraction of mineral oil containing an amount of dimeric acids effective to inhibit rusting of ferrous metals with which said composition is in contact. The dimeric acids are dicarboxylic acids selected from the group consisting of (1)'j dicarboxylic acids having one siX-mem-bered hydroaromatic ring having two alkyl groups in im-- mediately adjacent positions and two 'carboxyl groups one of which is attached to said hydroaromatic ring through a straight chain unsat' urated aliphatic group having the double bond adjacent to said ring and the other carboxyl group being attached'to said ring through a straight chain. saturated: aliphaticv group and t2) dicarboxylic acids having two fusedv.sixmembered hydroaromatic rings to one of which are attached two straight chain unsaturated 'ali-' phatic groups in immediatelyadjacent positions and to the other ring two carboxylic acid groups are attached in immediately adjacent-positionsthrough two straight chain aliphatic groups. The dimeric acids are dicarboxylic acids de rived from two molecules of .polyethenoid fattyf acids of drying and semi-drying .oils and from fatty acids such as ricinoleic acid which upon dehydration become polyethenoid jfatty acids. Therefore, in general, dimericiacids' zare dicarboxylic acids derived by the condensation'oftwo '17 molecules one or more polyethenoid aliphatic monocarboxylic acid.

While the dimeric acids can be used in pure form, for practical reasons impure forms are used. That is to say, the dimeric acids are not presently available at commercially attractive costs in pure form. The purest form examined contained about 85% dimeric acids-the impurest sample examined contained about 45% dimeric acids. Accordingly, it is to be understood that in the data presented hereinbefore the concentrations of dimeric acids given therein are values based upon the impure dimeric acids uncorrected for concentration of dimeric acids present in the mixture. Thus, the addition of 0.001% of either Emery Industries Inc. dimer acids or castor oil polymer acids were equally eifective although the castor oil polymer acids contained only about 45% dimeric acids and the balance higher polymeric acids while the Emery Industries Inc. dimer acids contained about 85% dimeric acids and about 12% higher polymeric acids.

While the structural formulae can be written for the dimeric acids produced when only one polyethenoid aliphatic monocarboxylic acid is present in the mixture undergoing polymerization, it is manifest that a generic structural formula cannot be written for the dimeric acids produced when a mixture of polyethenoid aliphatic monocarboxylic acids is polymerized. This is self-evident from a consideration of the previous discussion of the effect of the positions of the double bonds of the monocarboxylic acid upon the length of the substituent groups. Accordingly, the rust inhibiting material of the present invention is defined simply as dimeric acids in accordance with Goebels usage in U. S. Patent No. 2,482,761 or as dimeric acids produced by the condensation of two molecules of polyethenoid aliphatic monocarboxylic acids.

This application is a continuation-in-part of co-pending application, Serial No. 125,844, filed November 5, 1949, now abandoned.

We claim:

1. A normally liquid, non-lubricating mineral oil fraction containing a minor proportion, sufilcient to prevent rusting of ferrou metal surfaces in contact therewith, of an antirust agent selected from the group consistin of (1) dimeric acids produced by the condensation of unsaturated, aliphatic monocarboxylic acids having between about 16 and about 18 carbon atoms per molecule, (2) dimeric acids produced by the condensation of hydroxyaliphatic monocarboxylic acids having between about 16 and about 18 carbon atoms per molecule, (3) trimeric acids produced by the condensation of unsaturated, aliphatic monocarboxylic acids having between about 16 and about 18 carbon atoms per molecule, (4) trimeric acids produced by the condensation of hydroxyaliphatic monocarboxylic acids having between about 16 and about 18 carbon atoms per molecule.

2. A normally liquid, non-lubricating mineral oil fraction containing between about 0.0006 per cent and about 0.008 per cent, by weight, of an antirust agent selected from the group consisting of (1) dimeric acids produced by the condensation of unsaturated, aliphatic monocarboxylic acids having between about 16 and about 18 carbon atoms per molecule, (2) dimeric acids produced by the condensation of hydroxyaliphatic monocarboxylic acids having between about 16 and about 18 carbon atoms per molecule, (3) trimeric acids produced by the condensation of unsaturated, aliphatic monocarboxylic acids having between about 16 and about 18 carbon atoms per molecule, (4) trimeric acids produced by the condensation of hydroxyaliphatic monocarboxylic acids having between about 16 and about 18 carbon atoms per molecule.

3. A normally liquid, non-lubricating fraction of mineral oil containing between about 0.0006 per cent and about 0.008 per cent, by weight, of essentially dimerized linseed oil fatty acids having the following characteristics:

Neutral equivalent 290-310 Iodine value -95 Dimeric acid Approx. Trimeric acid and higher polymers- Approx. 12% Monomeric acid Approx. 3%

4. A normally liquid, non-lubricating fraction of mineral oil containing between about 0.0006 per cent and about 0.008 per cent, by weight, of essentially dimerized castor oil fatty acids having the following characteristics:

Neutralization No 159-164 Bromine No 19-21 Dimeric acid About 45-50% Trimeric acid and higher polymers Balance 5. A composition as defined in claim 3 where- PHILLIP S. LANDIS. ELWOOD B. BACKENSTO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Von Fuchs Nov. 9, 1943 Number 

1. A NORMALLY LIQUID, NON-LUBRICATING MINERAL OIL FRACTION CONTAINING A MINOR PROPORTION, SUFFICIENT TO PREVENT RUSTING OF FERROUS METAL SURFACES IN CONTACT THEREWITH, OF AN ANTIRUST AGENT SELECTED FROM THE GROUP CONSISTING OF (1) DIMERIC ACIDS PRODUCED BY THE CONDENSATION OF UNSATURATED, ALIPHATIC MONOCARBOXYLIC ACIDS HAVING BETWEEN ABOUT 16 AND ABOUT 18 CARBON ATOMS PER MOLECULE, (2) DIMERIC ACIDS PRODUCED BY THE CONDENSATION OF HYDROXYALIPHATIC MONOCARBOXYLIC ACIDS HAVING BETWEEN ABOUT 16 AND ABOUT 18 CARBON ATOMS PER MOLECULE, (3) TRIMERIC ACIDS PRODUCED BY THE CONDENSATION OF UNSATURATED, ALIPHATIC MONOCARBOXYLIC ACIDS HAVING BETWEEN ABOUT 16 AND ABOUT 18 CARBON ATOMS PER MOLECULE, (4) TRIMERIC ACIDS PRODUCED BY THE CONDENSATION OF HYDROXYALIPHATIC MONOCARBOXYLIC ACIDS HAVING BETWEEN ABOUT 16 AND ABOUT 18 CARBON ATOMS PER MOLECULE. 